Method for adaptively driving a tracking element with mechanical deviation and device using the same

ABSTRACT

The present invention provides a method for adaptively driving a tracking element with mechanical deviation and a driving device using the same. The method comprises the following steps: recording standard moving time and a standard motor current value, supplying driving voltage to a motor for driving a tracking element, detecting a current value of the motor and detecting moving time of the tracking element, and adjusting a driving gain of the motor based on the relation between the current value of the motor and the standard motor current value, and based on the relation between the moving time of the tracking element and the standard moving time of the standard one.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Taiwan applicationserial no. 94140561, filed on Nov. 18, 2005. All disclosure of theTaiwan application is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for driving a tracking elementand a driving device using the same. More particularly, the presentinvention relates to a method for adaptively driving a tracking elementwith mechanical deviation and a driving device using the same.

2. Description of Related Art

FIG. 1A is a view of a driving mechanism of a conventional optical discdrive. The mechanism of the optical disc drive includes a transmissionbar 101, an optical head 102, a mirror mount 103, a tracking gear set104, and a sledge tracking motor 105. The sledge tracking motor 105pushes the optical head 102 to move along the transmission bars 101through the tracking gear set 104. The mirror mount 103 is disposed onthe optical head 102 for focusing the light beams emitted from insidethe optical head 102 to access data. FIG. 1B is a motion graph of thedriving mechanism of a conventional optical disc drive. In general, asthe optical disc 107 has a large number of tracks, dual stoppers areusually used to reduce the moving time of the optical head 102 to theposition to be read. First, the optical head 102 is forced to move alonger distance, for example, across hundreds of tracks, by the sledgetracking motor 105. Next, the mirror mount 103 is forced to move ashorter distance, for example, less than a track, by the stopper 106inside the optical head, so as to reduce the reading time and improvethe precision by division of work.

Referring to FIGS. 1A and 1B, in order to move the mirror mount 103 tothe position SD to read the data in the optical disc 107, generally theoptical head 102 is forced to move from the position SA to SB by thesledge tracking motor 105. Next, the mirror mount 103 is forced to movefrom the position SC to SD by the stopper 106 inside the optical head.In general, the principle of the motion mechanism of the optical discdrive is to supply the voltage to the sledge tracking motor 105. Whenthe sledge tracking motor 105 is initiated, the tracking gear set 104 isdriven to bring the optical head 102 gliding on the transmission bars101. Therefore, the optical head 102 is forced to move a long distance,for example, across hundreds of tracks. Next, the stopper 106 inside theoptical head (usually a voice coil motor) pushes the mirror mount 103moving a short distance according to the principle of electromagneticinduction, so as to track more precisely.

When the optical head 102 is moving, in order to make the optical head102 reach the predetermined position, track crossing signals on theoptical disc 107 are detected (i.e., using the radio frequency (RF) andthe tracking error (TE) signals for mutual determination) for correctingthe position and speed. However, when the friction changes, for example,the friction increases due to the bad engagement of the gear set, theopen loop cannot compensate completely. Therefore, the optical discdrive adopting such a gear set is regarded as unqualified.

SUMMARY OF THE INVENTION

An object of the invention is to provide a method for adaptively drivinga tracking element with mechanical deviation. The method can overcomepoor performance of the tracking servo due to variance factors such asthe assembly difference of the tracking element (for example, thedifference of the assembly position between the transmission gear andthe sledge motor gear during the assembly), aging of the trackingelement (for example, the deformation of the gear after a long-termusage), the manufacturing difference of the element (for example, thespecification difference of the shape of the gear), expansion due toheat and contraction due to cold or change of in the viscositycoefficient of the lubricant oil due to environmental changes (forexample, different temperature and humidity).

Another object of the invention is to provide a driving device foradaptively driving a tracking element with mechanical deviation. Thisdevice can overcome poor performance of the tracking servo due to thevariance factors such as the assembly difference of the trackingelement, aging variance of the tracking element, the manufacturingdifference of the element, the environmental change factors.

In accordance with the above and other objects of the present invention,a method for adaptively driving a tracking element with mechanicaldeviation is provided. In the method, a tracking element is driven by amotor, and the method for driving the tracking element includes thefollowing steps. First, the standard moving time of a standard trackingelement and the standard motor current value are recorded. A drivingvoltage is supplied to a motor for driving a tracking element. Thecurrent value of the motor and the moving time of the tracking elementare detected. And then, a driving gain of the motor based on therelation between the current value of the motor and the standard motorcurrent value are adjusted based on the relation between the moving timeof the tracking element and the standard moving time of the standardone.

The method for adaptively driving a tracking element with mechanicaldeviation according to the preferred embodiment of the invention furtherincludes supplying a standard driving voltage to a standard motor fordriving a standard tracking element to track back and froth once;detecting the current value of the standard motor as the standard motorcurrent value; and detecting the moving time of the standard trackingelement as the standard moving time. The step of recording the standardmoving time and the standard motor current value includes recording thestandard moving time and the standard motor current value into anon-volatile memory. And the step of adjusting a driving gain of themotor includes raising the driving voltage when the current value of themotor is larger than the standard current value; supplying the raiseddriving voltage to the motor for driving a tracking element to trackback and froth once; detecting the moving time of the tracking element;and comparing the moving time of the tracking element and the standardmoving time to ascertain whether they are equal. However, when themoving time of the tracking element approaches the standard moving time,the proportion of increasing the driving gain of the motor is determinedby the proportion of the raised driving voltage and the standard drivingvoltage.

According to an aspect of the present invention, the step of adjusting adriving gain of the motor includes reducing the driving voltage when thecurrent value of the motor is lower than the standard current value;supplying the reduced driving voltage to the motor for driving thetracking element to track back and froth once; detecting the moving timeof the tracking element, and comparing the moving time of the trackingelement and the standard moving time to ascertain whether they areequal. When the moving time of the tracking element approaches thestandard moving time, the proportion of reducing the driving gain of themotor is determined by the proportion between the reduced drivingvoltage and the standard driving voltage. The method for adaptivelydriving a tracking element with mechanical deviation can be applied tothe tracking mechanism of an optical disc drive, and the trackingelement includes a sledge tracking element.

According to another aspect of the present invention, a device foradaptively driving a tracking element with mechanical deviation isadopted for controlling a motor to drive a tracing element. The drivingdevice of the tracking element includes a memory, a motor driver, acurrent detecting circuit and a processor. The memory is used to recordthe standard moving time and the standard current value. The motordriver, electrically connected to the motor is used to output thedriving voltage to the motor in accordance with the control signal fordriving the tracking element. The current detecting circuit iselectrically connected to the motor for detecting the current of themotor to be adjusted. The processor is electrically connected to thememory, the motor driver and the current detecting circuit foroutputting control signal to control the motor driver and measuring themoving time of the tracking element. The processor controls the motordriver to adjust the driving gain of the motor based on the relationbetween the current value of the motor measured by the current detectingcircuit and the standard motor current value recorded in the memory, andbased on the relation between the moving time of the tracking elementand the standard moving time.

According to an aspect of the present invention, the standard drivingvoltage is supplied to a standard motor for driving the standardtracking element to track back and froth once for detecting the currentvalue of the standard motor as the standard motor current value, andthen the moving time of the standard tracking element as the standardmoving time is detected. The memory can be a non-volatile memory. Whenthe current value of the motor is higher than the standard currentvalue, the processor controls the motor driver to raise the drivingvoltage and supplies the raised driving voltage to the motor for drivingthe tracking element to track back and froth once to detect the movingtime of the tracking element.

According to an aspect of the present invention, when the processorcompares and determines that the moving time value of the trackingelement is not the same as the standard moving time value, the drivingvoltage is raised again and the moving time of the tracking element iscompared with the standard moving time, wherein when the moving timevalue of the tracking element approaches the standard moving time value,the proportion of increasing the driving gain of the motor is determinedby the proportion between the increased driving voltage and the standarddriving voltage. When the current value of the motor is smaller than thestandard current value, the processor controls the motor driver toreduce the driving voltage, and supplies the reduced driving voltage tothe motor for driving the tracking element to track back and froth once,so as to detect the moving time of the tracking element. Then, when theprocessor compares and detects that the moving time value of thetracking element is not the same as the standard moving time value, thedriving voltage is reduced again and the moving time of the trackingelement is compared with the standard moving time. And, when the movingtime value of the tracking element approaches the standard moving timevalue, the proportion of reducing the driving gain of the motor isdetermined by the proportion between the decreased driving voltage andthe standard driving voltage. The device for adaptively driving atracking element with mechanical deviation can be applied to thetracking mechanism of an optical disc drive. The tracking elementincludes a sledge tracking element.

As the controller gain of the motor is adjusted according to the loadcurrent value of the standard motor by detecting the changes of the loadcurrent of the motor, the variance factors affecting the performance ofthe tracking servo, such as the assembly position difference due to theassembly of the tracking element, the deformation caused due to theaging of the tracking element, the specification difference of themanufactured form of the element, expansion due to heat and contractiondue to cold or the change of the viscosity coefficient of the lubricantoil caused by the environmental factors may be effectively reduced.

In order to the make the aforementioned and other objects, features andadvantages of the present invention comprehensible, a preferredembodiment accompanied with figures is described in detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a reference diagram of a driving mechanism of a conventionaloptical disc drive.

FIG. 1B is a graph showing the motion of the driving mechanism of aconventional optical disc drive.

FIG. 2 is a circuit diagram illustrating the tracking DC motor 200.

FIG. 3 is a flow chart illustrating the recording of the standard movingtime and the current value of the standard DC motor according to theembodiment of the invention.

FIG. 4 is a timing diagram of detecting the load degree of the trackingDC motor.

FIG. 5 is a flow chart of the method for adaptively driving a trackingelement with mechanical deviation according to the embodiment of theinvention.

FIG. 6 is a circuit block view of the device for adaptively driving atracking element with mechanical deviation and a sledge tracking DCmotor.

DESCRIPTION OF EMBODIMENTS

FIG. 2 is an equivalent circuit diagram illustrating a tracking DC motor200. The circuit of the DC motor can be represented by the followingexpression:

$\begin{matrix}{{Va} = {{{Ra} \cdot {ia}} + {{La} \cdot \frac{\mathbb{d}{ia}}{\mathbb{d}t}} + {Ea}}} & (1)\end{matrix}$

-   -   where, Va represents the voltage at both ends of the DC motor        200; Ra represents the armature resistance; La represents        armature inductance; ia represents the current value passing        through Ra; t represents time; and

$\left( \frac{\mathbb{d}{ia}}{\mathbb{d}t} \right)$represents a differential of the current value ia to the time t. Theexpression indicates the voltage distribution inside the tracking DCmotor 200. Then, assuming the armature inductance La of the tracking DCmotor 200 is 0, the expression (1) is simplified to be the followingexpression:Va =Ra·ia +Ea  (2)The back electromotive force Ea of the tracking DC motor 200 can berepresented by the following expression:Ea =Kb·ω  (3)where, Kb represents back electromotive force coefficient, and ωrepresents the rotational angular speed of the motor. The angular speedω affects the back electromotive force Ea.

When a constant voltage Va is supplied to the tracking DC motor 200, thetracking DC motor 200 has a constant rotational angular speed ω underthe constant friction. Referring to expressions (2) and (3) at the sametime, under the constant voltage Va, if the rotational angular speed ωof the tracking DC motor 200 is reduced due to the over friction, theback electromotive force Ea is reduced accordingly. However, under thecondition of constant voltage Va, the current value ia is increased. Onthe other hand, if the angular speed ω of the tracking DC motor 200 isincreased due to the reduced friction, the back electromotive force Eais increased, and under the constant voltage Va, the current value ia isreduced. Therefore, the changes of the friction can be obtained bydetecting the changes of the current value ia.

FIG. 3 is a flow chart illustrating the recording of the standard movingtime and the current value of the standard tracking DC motor accordingto the embodiment of the invention. First, in Step S301, the standardmechanism is sampled and the tracking motor starts to detect. Thestandard mechanism comprises, for example, a standard motor and astandard tracking element (elements such as a transmission shaft,tracking gear required for moving the optical head) of an optical discdrive. As the standard transmission shaft and the standard tracking gearset are sophisticated and well assembled, a desired tracking time isachieved in reaching the desired track. Next, in Step S303, the standarddriving voltage VS is supplied to a standard motor for driving astandard tracking element to track back and froth once, and detectingthe average current value of the standard motor as the standard currentvalue iS and the moving time as the standard moving time TS. In StepS303, the design of the tracking element moving back and froth once isthat the tracking system moves in the same mechanism model, so themoving distance is fixed. The moving time of the tracking element isdetected under the circumstance that the tracking element moves a fixeddistance, thereby deducing the condition of the moving speed of thetracking element under the influence of friction. Next, in Step S305,the standard current value iS and the standard moving time TS arerecorded and stored in a memory, such as a non-volatile memory. Thestored standard current value iS and the standard moving time TS can betaken as a reference when adjusting the voltage gain of other trackingDC motors during mass production, thereby achieving a better trackingperformance of various motors. Meanwhile, when the tracking elementages, the standard current value and the standard moving time can alsobe used as the standard for adjusting the tracking motor of the agingtracking element. The viscosity coefficient of the lubricant oil of thetracking element is influenced by the temperature and humidity indifferent environmental conditions (for example, the area in thelatitude far from the producing area), so that the standard data canalso be the reference for adjusting.

FIG. 4 is a timing diagram of detecting the load degree of the trackingDC motor. Referring to the aforementioned expressions (2), (3) and FIG.4, the scheme of detecting the current value of the motor and the movingtime of the tracking element is illustrated. FIG. 4 indicates thecorresponding relation of the voltage Va of the tracking DC motor, thecurrent value ia of the tracking DC motor and the clock signal. Duringthe time period 0˜TA, as the tracking element has not moved, the angularspeed of the motor is 0 and the current value remains the maximum i1.During the time period TA˜TB, as the tracking element starts to move,the rotational angular speed of the motor is increased and the backelectromotive force of the motor is increased. While under the constantvoltage V1, the current value at this time is reduced to i2. During thetime period TB˜TC, the tracking element has moved to the outermost trackand will stop due to the limitation of the length of the trackmechanism, and then the tracking element is at a fixed position.Therefore, the rotational angular speed of the tracking element returnsto 0 as the tracking element stops moving, and the current value returnsto its maximum i1. As a result, the moving time of the tracking elementis represented as TA ˜TB, and the current value when the motor pushesthe tracking element is represented as i2.

FIG. 5 is a flow chart of a method for adaptively driving a trackingelement with mechanical deviation according to the embodiment of theinvention. First, in Step S501, the standard moving time TS and thestandard current value iS are recorded, by referring to Steps S301˜S305of recording the standard moving time and the standard motor currentvalue of the standard tracking DC motor in FIG. 3. In Step S502, thecurrent value of the tracking motor of the mechanism from massproduction is recorded. In Step S503, the driving voltage Va (theinitial value is, for example, the standard voltage VS ) is supplied tothe motor for driving the tracking element to track in and out once, andthen detecting the average current value iA of the motor and the movingtime T. Thus, in Step S505, the average current value iA of the motorfrom mass production and the average current value iS of the standardmotor are compared to see whether they are equal. If the average currentvalue iA of the motor is equal to the average current value iS of thestandard motor, the procedure proceeds to Step S507, indicating that theadjusting operation is completed without correcting the gain of themotor in the tracking system. If the average current value iA of themotor and the average current value iS of the standard motor are notsame, then the procedure proceeds to Step S509 for furtherdetermination.

In Step S509, the average current value iA of the motor and the averagecurrent value iS of the standard motor are compared. When the averagecurrent value iA of the motor is larger than the average current valueiS of the standard motor, the angular speed of the motor is reduced dueto the increase of the friction, and then proceed to Step S511, i.e.,raising the driving voltage Va of the motor for driving the trackingelement to track in and out once again and detecting the average currentvalue iA of the motor and the moving time T. Thereafter, in Step S513,the moving time T and the standard moving time TS are compared to seewhether they are equal. When the moving time T are not the same as thestandard moving time TS, the procedure returns to Step S511 to increasethe voltage Va again until the moving time T is equal the standardmoving time TS. When the moving time T is equal to the standard movingtime TS, the driving voltage Va of the motor is the final voltage Va_f.In Step S515, the proportion of raising the voltage of the trackingmotor (Va_f/VS) can be obtained based on the final voltage Va_f and thestandard voltage VS. The proportion of increasing the driving gain ofthe motor is determined by the proportion of raising the voltage, i.e.,the driving voltage levels supplied to the tracking motor during thenormal operation are all amplified in the same proportion. When thefriction of the gears of the tracking element is increased due to thesmall gear backlash during the manufacture, the voltage can also beadjusted by the driving method, thus the tracking element withmechanical deviation functions properly.

In the above Step S509, if the comparison result is the average currentvalue iA of the motor smaller than the average current value iS of thestandard motor, the procedure proceeds to Step S517. In Step S517, thedriving voltage Va of the motor is reduced for driving the trackingelement to track in and out once again, and detects the average currentvalue iA of the motor and the moving time T. Next, in Step S519, themoving time T and the standard moving time TS are compared to ascertainwhether they are equal. When the moving time T and the standard movingtime TS are not equal, the procedure returns to Step S517 to reduce thevoltage Va until the moving time T is equal to the standard moving timeTS. When the moving time T is equal to the standard moving time TS, thedriving voltage Va is the final voltage Va_f. In Step S521, theproportion of reducing the voltage of the tracking motor (Va_f/VS) canbe obtained based on relation between the final voltage Va_f and thestandard voltage VS. Also, the proportion of reducing the driving gainof the motor is determined by the proportion of reducing the voltage,i.e., the driving voltage levels supplied to the tracking motor duringthe normal operation are all reduced in the same proportion.

The driving method according to the above embodiment can be used fordriving the tracking mechanism of an optical disc drive, such as asledge tracking element. Besides, in the aforementioned embodiment, theabove adjustment mechanism can be initiated as desired. Therefore, themethod for driving a tracking element can overcome the assembly positionvariance occurring during the assembly of the tracking element (forexample, the over-sized gear backlash of the tracking gear set of thetracking element), thereby remarkably increasing the product yield.Moreover, the method for driving a tracking element according to theabove embodiment can also overcome the influences caused by variancefactors such as the deformation due to the aging of the trackingelement, the specification difference of the manufactured form of theelement, expansion due to heat and contraction due to cold or the changeof the viscosity coefficient of the lubricant oil caused by theenvironmental conditions, thereby adaptively and promptly adjust thedriving gain of the motor.

FIG. 6 is a circuit block view of the device for adaptively driving atracking element with mechanism difference and a sledge tracking DCmotor according to the embodiment of the invention. By reference, thedevice 61 for adaptively driving a tracking element with mechanicaldeviation controls the sledge DC motor 62 to drive the tracking element(not shown). The driving device 61 includes a memory 601, a motor driver602, a current detecting circuit 603, and a processor 604. The memory601 is used to record the standard moving time and the standard currentvalue. The motor driver 602 is electrically connected to the sledgetracking DC motor 62 for outputting the corresponding driving voltageaccording to the control signal and supplying the driving voltage to thesledge tracking DC motor 62 to drive the tracking element. The currentdetecting circuit 603 is electrically connected to the sledge trackingDC motor 62 for detecting the current value of the tracking DC motor 62.The processor 604 is electrically connected to the memory 601, the motordriver 602, the current detecting circuit 603, for controlling the motordriver 602 by outputting control signals, and measuring the moving timeof the tracking element. The processor 604 controls the motor driver 602to adjust the driving gain of the sledge tracking DC motor 62 based onthe relation between the current value of the sledge tracking DC motor62 detected by the current detecting circuit 603 and the standardcurrent value recorded in the memory 601, and based on the relationbetween the moving time of the tracking element and the standard movingtime recorded in the memory 601.

The memory 601 of the driving device 61 can be a non-volatile memory.The standard moving time and the standard current value stored in thememory 601 are resulted from supplying the standard driving voltage tothe standard motor for driving the standard tracking element to trackback and froth once and detecting the current value of the standardmotor as the standard motor current value, and detecting the moving timeof the standard tracking element as the standard moving time.

After detection by the current detecting circuit 603, when the currentvalue of the sledge tracking DC motor 62 is larger than the standardmotor current value, the processor 604 controls the motor driver 602 toraise the driving voltage, and supplies the raised driving voltage tothe sledge tracking DC motor 62 for driving the tracking element totrack back and froth once, thereby detect the moving time of thetracking element. Then, when the processor 604 compares and determinesthat the moving time of the tracking element is not equal to thestandard moving time, the driving voltage is raised again and the movingtime of the tracking element is compared with the standard moving timeuntil the moving time is equal to the standard moving time. When themoving time of the tracking element is equal to the standard movingtime, the proportion of increasing the driving gain of the motor isdetermined by the proportion between the raised driving voltage and thestandard driving voltage.

After detection by the current detecting circuit 603, when the currentvalue of the sledge tracking DC motor 62 is smaller than the standardmotor current value, the processor 604 controls the motor driver 602 toreduce the driving voltage, and supplies the reduced driving voltage tothe sledge tracking DC motor 62 for driving the tracking element totrack back and froth once, thereby detect the moving time of thetracking element. Then, when the processor 604 compares and determinesthat the moving time of the tracking element is not equal to thestandard moving time, the driving voltage is reduced again and themoving time of the tracking element is compared with the standard movingtime until the moving time is equal to the standard moving time. Whenthe moving time of the tracking element is equal to the standard movingtime, the proportion of reducing the driving gain of the motor isdetermined by the proportion between the reduced driving voltage and thestandard driving voltage.

The tracking element can be a sledge tracking element. The device foradaptively driving a tracking element with mechanical deviation can beapplied to drive the tracking system of an optical disc drive. However,those skilled in the art should understand the application of theinvention is not limited to this and any servo parameters using thechanges of the current passing through the tracking DC motor to deducethe friction between the gears and adjust the tracking system fallwithin the scope of the invention.

In view of the above, the method for adaptively driving a trackingelement with mechanical deviation and device using the same is adoptedfor comparing the moving time of the standard tracking element with themoving time of the tracking element to be adjusted and comparing thecurrent value of the motor to continuously adjust the voltage gain ofthe motor by supplying different voltages according to differentdetection results. Therefore, the problems influencing the performanceof the tracking element such as the assembly difference, manufacturingdifference, differential environmental conditions, and element aging canbe overcome. Thus, the product yield, the tracking quality and servicelife of the tracking element can be effectively increased.

Though the present invention has been disclosed above by the preferredembodiments, it is not intended to limit the invention. Anybody skilledin the art can make some modifications and variations without departingfrom the spirit and scope of the invention. Therefore, the protectingrange of the invention falls in the appended claims.

1. A device for adaptively driving a tracking element of an optical discdrive with mechanical deviation, suitable for controlling a motor todrive the tracking element, the device comprising: a memory, forrecording a standard moving time relating to the tracking element movingwithin a fixed distance along a moving path; a motor driver,electrically connected to the motor, for outputting a driving voltage tosupply the motor for driving the tracking element in accordance with acontrol signal; a current detecting circuit, electrically connected tothe motor, for detecting a first current value of the motor; and aprocessor, electrically connected to the memory, the motor driver andthe current detecting circuit, the processor is configured foroutputting the control signal to the motor driver and measuring a firstmoving time of the tracking element moving along the fixed distance,wherein the processor controls the motor driver to adjust a voltage gainof the motor based on the relation between the first current valuemeasured by the current detecting circuit and a standard motor currentvalue recorded in the memory, and based on the relation between thefirst moving time and the standard moving time.
 2. The device foradaptively driving a tracking element with mechanical deviationaccording to claim 1, wherein a standard driving voltage is supplied toa standard motor for driving a standard tracking element to track backand forth once along the moving path to detect a second current value ofthe standard motor as the standard motor current value, and detect asecond moving time of the standard tracking element as the standardmoving time.
 3. The device for adaptively driving a tracking elementwith mechanical deviation according to claim 1, wherein the memory is anon-volatile memory.
 4. The device for adaptively driving a trackingelement with mechanical deviation according to claim 1, wherein when thefirst current value is larger than the standard motor current value, theprocessor controls the motor driver to raise the driving voltage, andsupply the driving voltage to the motor for driving the tracking elementto track back and forth once to detect the first moving time; when theprocessor compares and determines that the first moving time is notequal to the standard moving time, the driving voltage is raised againand the first moving time is compared with the standard moving time; andwhen the first moving time is equal to the standard moving time, aproportion of increasing the voltage gain of the motor is determined bythe proportion between the driving voltage and the standard drivingvoltage.
 5. The device for adaptively driving a tracking element withmechanical deviation according to claim 1, wherein when the firstcurrent value is smaller than the standard motor current value, theprocessor controls the motor driver to reduce the driving voltage, andsupply the driving voltage to the motor for driving the tracking elementto track back and forth once to detect the first moving time; when theprocessor compares and determines that the first moving time is equal tothe standard moving time, the driving voltage is reduced again and thefirst moving time is compared with the standard moving time; and whenthe first moving time is equal to the standard moving time, a proportionof reducing the voltage gain of the motor is determined by theproportion between the driving voltage and the standard driving voltage.6. The device for adaptively driving a tracking element with mechanicaldeviation according to claim 1, wherein the device is applicable indriving a tracking mechanism of an optical disc drive.
 7. The device foradaptively driving a tracking element with mechanical deviationaccording to claim 1, wherein the tracking element is a sledge trackingelement.
 8. A method for adaptively driving a tracking element of anoptical disc drive with mechanical deviation by a motor, the methodcomprising: recording a standard moving time relating to the trackingelement moving within a fixed distance along a moving path; supplying adriving voltage to the motor for driving the tracking element; detectinga first current value of the motor and estimating a first moving timefrom the first current value, at a processor, relating to the trackingelement moving within the fixed distance of the tracking element; andadjusting a voltage gain of the motor based on the relation between thefirst current value and a standard motor current value, and based on therelation between the first moving time and the standard moving time,wherein when the first current value is larger than the standard motorcurrent value. raising the driving voltage; supplying the drivingvoltage to the motor for driving the tracking element to track back andforth once; detecting the first moving time; comparing the first movingtime and the standard moving time to ascertain whether they are equal;and increasing the voltage gain of the motor according to a proportionbetween the driving voltage and a standard driving voltage when thefirst moving time of the tracking element is equal to the standardmoving time.
 9. The method for adaptively driving a tracking elementwith mechanical deviation by a motor according to claim 8, furthercomprising: supplying a standard driving voltage to a standard motor fordriving a standard tracking element to track back and forth once alongthe moving path; detecting a second current value of the standard motoras the standard motor current value; and detecting a second moving timeof the standard tracking element as the standard moving time.
 10. Themethod for adaptively driving a tracking element with mechanicaldeviation by a motor according to claim 8, wherein the step of recordingthe standard moving time and the standard motor current value comprises:recording the standard moving time and the standard motor current valuein a non-volatile memory.
 11. The method for adaptively driving atracking element with mechanical deviation by a motor according to claim8, wherein the step of adjusting a voltage gain of the motor furthercomprises: repeating the step of raising the driving voltage until thefirst moving time is equal to the standard moving time when the firstmoving time is not equal to the standard moving time.
 12. The method foradaptively driving a tracking element with mechanical deviation by amotor according to claim 8, wherein the step of adjusting a voltage gainof the motor comprises: when the first current value is smaller than thestandard motor current value, reducing the driving voltage; supplyingthe driving voltage to the motor for driving the tracking element totrack back and forth once; detecting the first moving time; comparingthe first moving time and the standard moving time to ascertain whetherthey are equal; and reducing the voltage gain of the motor according toa proportion between the driving voltage and the standard drivingvoltage when the first moving time of the tracking element is equal tothe standard moving time.
 13. The method for adaptively driving atracking element with mechanical deviation by a motor according to claim12, wherein the step of adjusting a voltage gain of the motor furthercomprises: when the first moving time is not equal to the standardmoving time, repeating the step of reducing the first current valueuntil the first moving time is equal to the standard moving time. 14.The method for adaptively driving a tracking element with mechanicaldeviation by a motor according to claim 8, wherein the method issuitable for being applied in the tracking mechanism of an optical discdrive.
 15. The method for adaptively driving a tracking element withmechanical deviation by a motor according to claim 8, wherein thetracking element is a sledge tracking element.